The screw retainer of the present invention is used in conjunction with a molded case circuit breaker movable contact arm arrangement that is described in commonly assigned U.S. Pat. No. 4,931,603, issued Jun. 5, 1990, entitled "Molded Case Circuit Breaker Movable Contact Arm Arrangement". The Patent describes a molded case circuit breaker movable contact arm that is positioned within the circuit breaker case by means of a support base that includes integrally-formed upstanding support arms. The movable contact arm is mechanically and electrically connected between the upstanding support arms. The movable contact arm utilizes a shaped antiturn screw retainer which includes an integrally-formed H-shaped top part with a pair of oppositely depending legs. The screw retainer is formed from a spring metal with legs cantilevered toward each other and having radial-shaped ends. The screw retainer has a through-hole formed in the H-shaped top part to receive and retain a support screw. The support base is formed to provide an offset end having a through-hole, that accepts the support screw that is utilized to fasten the support base to a circuit breaker load strap.
During the manufacture of molded case circuit breaker components utilizing the screw retainer described within aforementioned U.S. Pat. No. 4,931,603 via robotic or automated systems, the screw retainer may become dislodged. This is typically the result of the motion of robotic arms utilized to engage the movable contact arm arrangement. Attaching a replacement screw retainer onto the movable contact arm arrangement once the movable contact arm arrangement is inserted into the molded case is difficult to accomplish.
Typically, the movable contact arm arrangement must be manually extracted in order to insert the replacement screw retainer. This is a time consuming process that degrades the efficiency of a robotic or automated manufacturing system.
In commonly assigned U.S. Pat. No. 4,650,272, issued Mar. 17, 1987, entitled "Circuit Breaker Line Terminal Screw Retainer", to Doughty, et al., there is described a composite line terminal strap that is used with a molded case circuit breaker to support a circuit breaker stationary contact and to retain a circuit breaker line terminal screw. The circuit breaker stationary contact is welded to the line strap within the circuit breaker at a first end and the line terminal screw is attached to an opposite end of the line strap by a through-hole in a spring-steel retainer which extends partially within the circuit breaker. The line terminal screw is tightly held within the through-hole of the retainer at the first end and the retainer itself is trapped between the bottom of the circuit breaker case and the line strap at the opposite end of the line strap.
One purpose of the present invention is to provide a screw retainer that is positioned on the support base, of the contact arm arrangement described in U.S. Pat. No. 4,931,603, in such a manner that it cannot become dislodged during the manufacturing process of a molded case circuit breaker.
It is another object of the invention to provide a screw retainer of very simple construction.
Other objects and advantages of the invention will appear from reading the following description of the invention, with reference to the accompanying drawings.